Recently, in order to realize a high-performance semiconductor device, techniques for reducing a wiring resistance and a capacitance between wirings have been developed, and as the technique for reducing the wiring resistance, there is a method of forming a Cu wiring by a damascene process. Also, as the technique for reducing the capacitance between wirings, a method that is capable of realizing an insulating film formed on a periphery of the Cu wiring, the insulating film having a low dielectric constant, is effective. Particularly, as the insulating film having a low dielectric constant, a porous insulating film having fine holes therein such as SiOC film is known.
Since the porous insulating film has a reduced film density so as to lower the dielectric constant, it has a disadvantage that, for example, its properties are remarkably changed when a Chemical Mechanical Polishing (CMP) process that the Cu wiring is embedded and formed in a surface of the insulating film is carried out, and then an oxide film formed on the exposed surface of the Cu wiring is removed by a plasma processing.
Consequently, as a conventional technique, a method of manufacturing a semiconductor device is proposed that an electrically conductive film is embedded in the surface of the SiOC film, and then an oxide film formed on the exposed surface of the electrically conductive film is removed by carrying out both a thermal reduction process using a reducing gas whose main component is hydrogen (H2) and a plasma processing containing a reducing gas. The technique is disclosed in, for example, JP-A-2007-67132.
According to the method of manufacturing a semiconductor device, after the thermal reduction process using a reducing gas whose main component is hydrogen (H2) is carried out, the plasma processing containing a reducing gas of NH3 and N2 is carried out, and consequently it is not needed to carry out the thermal reduction process to such an extent that the SiOC film and the electrically conductive film are damaged due to increase in heat by the above-mentioned thermal reduction process, so that the properties of SiOC film can be prevented from being changed.
However, a reduction reaction by the plasma processing containing a reducing gas acts on the surface of the electrically conductive film and simultaneously the SiOC film, and the change of properties occurs in the SiOC film, the change of properties including that Si—O—Si bonds and Si—CH3 bonds are broken and a plurality of Si—H and Si—OH are formed in the SiOC film, so that a problem is caused that defective adhesion between a diffusion-preventing layer for preventing Cu contained in the electrically conductive film from being diffused and the SiOC film, and increases in capacitance between wirings and in leakage current are generated.